The present invention relates to avionics, and more particularly to Terrain Awareness and Warning Systems (TAWS) and navigational systems.
A conventional altitude display for a terrain awareness system for a given aircraft provides a pilot with a visual display of the terrain having an altitude higher than the aircraft, as well as the terrain within some distance (e.g. 2000xe2x80x2) below an aircraft. If it appears that the aircraft is going to hit or travel relatively close to terrain, various alerts and warnings are generated. See, e.g., U.S. Pat. No. 6,138,060 to Conner et al. As used herein, warnings relate to more threatening conditions than alerts. Each may include audible, visual or other type of indications to a user.
One problem with conventional systems is false or nuisance alerts and warnings may be generated as the aircraft is preparing to land at a runway. That is, as the aircraft descends it will naturally appear to be headed towards terrain (the runway), and nuisance alerts and warnings may be generated. Furthermore, the terrain may still be displayed on the aviation display unit. As a result, the screen may be cluttered with non-threatening terrain data during landing.
The present invention, in certain embodiments, overcomes the disadvantages of the prior art noted above.
In one aspect, the invention is directed to a system for reducing nuisance alerts and warnings in a terrain awareness and warning system for an aircraft, including determining if the aircraft is within a predetermined geometric volume surrounding an airport. If the aircraft is within the geometric volume, then determining the aircraft""s current projected flight path for a selected distance or time and comparing it with at least one approach volume extending from a runway at the airport towards an outer boundary of the geometric volume. If the aircraft""s current projected flight path is such that the aircraft is expected to be within the approach volume and stay within the approach volume to the runway, then inhibiting selected alerts and warnings associated with non-threatening terrain.
In another aspect, the invention is directed to a terrain awareness and warning system for an aircraft comprising a display apparatus which displays terrain within a predetermined look-ahead region based on the aircraft""s current projected flight path and generates alerts and warnings for terrain in or proximate to the aircraft""s current projected flight path; and an inhibition module which inhibits at least one of said alerts, warnings and terrain display under at least the following conditions: the aircraft is within a predetermined geometric volume surrounding an airport, and the aircraft""s current projected flight path is such that the aircraft is expected to be within an approach volume that extends from a runway at the airport towards an outer boundary of the geometric volume and to stay within the approach volume to the runway.
In another aspect, the invention is directed to a method of navigating an aircraft to land on a runway, comprising determining if the aircraft is within a predetermined geometric volume surrounding an airport; if the aircraft is within the geometric volume, then determining the aircraft""s current projected flight path for a selected distance or time; comparing the aircraft""s current projected flight path with an approach volume extending from a runway at the airport towards an outer boundary of the geometric volume; if the aircraft""s current projected flight path is such that the aircraft is expected to be within the approach volume and stay within the approach volume to the runway, then indicating that the aircraft is on proper course for landing; and if the aircraft""s current projected flight path is such that the aircraft is not expected to within the approach volume or to stay within the approach volume to the runway, indicating that the aircraft is not on proper course for landing.
In another aspect, the invention is directed to a method of calculating an approach volume for a runway for use with a terrain awareness and warning system or navigation system in an aircraft, comprising (a) setting a predetermined geometric volume surrounding the runway; (b) selecting a location along said runway as a ground point intercept (GPI); (c) selecting a most preferred approach path glide slope angle;(d) selecting lateral boundaries for the approach volume; (e) considering a tentative lower approach path plane that intersects the GPI and extends to an outer boundary of the geometric volume at an angle that is a predetermined amount more acute than said approach path glide slope angle; (f) determining whether the tentative lower approach path plane clears all terrain from the GPI to the outer boundary of the geometric volume by a predetermined safety margin, and if so, selecting the tentative lower approach path plane as an actual lower approach path plane, and if not, increasing the approach path glide slope angle and repeating steps (e) and (f) until the actual lower approach path plane is selected; (g) selecting an upper approach path plane, which extends from a predetermined location on the runway toward the outer boundary of the geometric volume at angle selected such that the upper approach path plane represents a maximum desirable approach path for the approach path volume.
In another aspect, the invention is directed to a terrain awareness and warning system for an aircraft comprising means for displaying terrain within a predetermined look-ahead region based on the aircraft""s current projected flight path and generating alerts and warnings for terrain in or proximate to the aircraft""s current projected flight path; and means for inhibiting at least one of said alerts, warnings and terrain display under at least the following conditions: the aircraft is within a predetermined geometric volume surrounding an airport, and the aircraft""s current projected flight path is such that the aircraft is expected to be within an approach volume that extends from a runway at the airport towards an outer boundary of the geometric volume and to stay within the approach volume to the runway.
In another aspect, the invention is directed to a method of reducing at least one of nuisance alerts and warnings in a terrain awareness and warning system for an aircraft, comprising (a) determining if the aircraft is within a predetermined geometric volume surrounding an airport; (b) if the aircraft is within the geometric volume, then determining a current projected flight path for a selected distance or time for the aircraft; (c) comparing the aircraft""s current projected flight path with at least one approach volume extending from a runway at the airport towards an outer boundary of the geometric volume; and (d) if the aircraft""s current projected flight path is such that the aircraft is expected to intersect the approach volume, then determining whether, under selected parameters, the aircraft is capable of maneuvering within said approach volume so as to stay within the approach volume to the runway; (e) if the determination of step (d) is positive, then inhibiting at least one of selected alerts and warnings associated with terrain and repeating step (d); (f) if the determination of step (d) is negative, then reactivating any previously inhibited alerts and warnings of step (e).
Other aspects, objects and advantages will be apparent from the description that follows, including the figures and the claims.